How is life expectancy measured?

Cohort life expectancy

Cohort life expectancy shows the probability of a person dying at each age over the course of their lifetime. It refers to a group of people with the same year of birth.

Cohort life expectancy takes into account future mortality improvement, because this is realistic (and matters when assessing longevity-related liabilities). However, this means that cohort life expectancy is subjective. This is because it requires someone to make assumptions about how future mortality might improve.

Cohort figures are often regarded as being a more appropriate measure of how long a person of a given age would be expected to live, when compared with the alternative measure known as "period life expectancy" (see below).

Period life expectancy

Period life expectancy makes no allowance for future mortality improvements and is often used as an objective measure of average current longevity. Whenever life expectancy is quoted in a statistical context, it is often period life expectancy.

Period life expectancies are a useful measure of mortality rates actually experienced over a given period. They can provide a baseline against which to benchmark cohort life expectancies. For past years they provide an objective way of comparing trends in mortality over time, between areas of a country and with other countries. Official life tables in the UK and in other countries which relate to past years are generally period life tables for these reasons.

Period life expectancies tend to be lower than cohort life expectancies, because they do not include any assumptions about future improvements in mortality rates.

How long will I live? Try a Life expectancy calculator

There are a range of online calculators to provide you with an estimate for your likely lifespan.

Abaris

Abaris is a a direct-to-consumer online marketplace. Their life expectancy calculator is based on a statistical regression of 400,000 data samples and uses data collected by the US National Institute of Health and the AARP.

Aviva

The Aviva life expectancy calculator uses UK data. To calculate your life expectancy, you need to enter only your date of birth, gender, and the age at which you plan to retire. Interestingly, setting a later retirement age seems to increase longevity.